Integrated non-thermal plasma reactor-diesel particulate filter

ABSTRACT

An integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus  10  comprises a wall flow-type substrate  12  including a plurality of alternating high voltage  20  and ground electrode layers  22  and filter layers  24  disposed between said high voltage  20  and ground electrode layers  22 . Channels  34  extending through the electrode layers  20, 22  are plugged to prevent exhaust flow. A portion of the exhaust channels  18  extending through the filter layers  23  are plugged  26  such that each channel  18  is plugged only at one end  14  or  16 . During operation, a plasma is generated in the filter layers  24 . An exhaust stream  28  is passed through the filter channels  18  and nitrogen oxides in the exhaust stream  28  are converted in the plasma primarily to NO 2  while particulate matter in the exhaust stream  28  is captured in the porous channel walls  19 . The filter  24  is continuously regenerated by NO 2  formed in the plasma. NO byproduct from the filter regeneration is converted back into NO 2  via plasma.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Application No. 60/368,403 (Attorney Docket No. DP-305558), of David A. Goulette, et al., filed Mar. 28, 2002, entitled “Non Thermal Plasma Reactor/DPF,” which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] The present invention relates generally to combustion exhaust treatment and more particularly relates to an integral non-thermal plasma reactor-diesel particulate filter apparatus.

BACKGROUND OF THE INVENTION

[0003] Certain compounds in the exhaust stream of a combustion process, such as the exhaust stream from an internal combustion engine, are undesirable in that they are thought to produce adverse health effects and must be controlled in order to meet government emissions regulations. Among the regulated compounds are hydrocarbons, soot particulates, and nitrogen oxide compounds (NOx). There are a wide variety of combustion processes producing these emissions, for instance, coal-or oil-fired furnaces, reciprocating internal combustion engines (including gasoline spark ignition and diesel engines), gas turbine engines, and so on. In each of these combustion processes, control measures to prevent or diminish atmospheric emissions of these emissions are needed.

[0004] Industry has devoted considerable effort to reducing regulated emissions from the exhaust streams of combustion processes. In particular, it is now usual in the automotive industry to place a catalytic converter in the exhaust system of gasoline spark ignition engines to remove undesirable emissions from the exhaust by chemical treatment. Typically, a “three-way” catalyst system of platinum, palladium, and rhodium metals dispersed on an oxide support is used to oxidize carbon monoxide and hydrocarbons to water and carbon dioxide and to reduce nitrogen oxides to nitrogen. The catalyst system is applied to a ceramic substrate such as beads, pellets, or a monolith. When used, beads are usually porous, ceramic spheres having the catalyst metals impregnated in an outer shell. The beads or pellets are of a suitable size and number in the catalytic converter in order to place an aggregate surface area in contact with the exhaust stream that is sufficient to treat the compounds of interest. When a monolith is used, it is usually a cordierite honeycomb monolith and may be pre-coated with gamma-alumina and other specialty oxide materials to provide a durable, high surface area support phase for catalyst deposition. The honeycomb shape, used with the parallel channels running in the direction of the flow of the exhaust stream, both increases the surface area exposed to the exhaust stream and allows the exhaust stream to pass through the catalytic converter without creating undue back pressure that would interfere with operation of the engine.

[0005] When a spark ignition engine is operating under stoichiometric conditions or nearly stoichiometric conditions with respect to the fuel-air ratio (just enough oxygen to completely combust the fuel, or perhaps up to 0.3% excess oxygen), a “three-way” catalyst has proven satisfactory for reducing emissions. Unburned fuel (hydrocarbons) and carbon monoxide are oxidized consuming relatively small amount of oxygen, while oxides of nitrogen (NOx) are simultaneously reduced. However, it is desirable to operate the engine at times under lean burn conditions, with excess air, in order to improve fuel economy. Under lean burn conditions, conventional catalytic devices are not effective for reducing the NOx in the oxygen-rich exhaust stream.

[0006] A diesel engine has substantially lower fuel consumption than a spark ignition engine, particularly at light loads. The exhaust stream from a diesel engine also has substantial oxygen content, from perhaps about 2-18% oxygen, and, in addition, contains a significant amount of particulate emissions. The particulate emissions, or soot, are thought to be primarily carbonaceous particles and volatile organic compounds (VOC). While diesel combustion process developments have been made that successfully decrease the total mass of particulates emitted, these modifications may have actually increased the numbers of smaller nanoparticles which are a particular health concern as they can travel deep into the lungs.

[0007] In spite of efforts over the last decade to develop an effective catalyst for reducing NOx to nitrogen under oxidizing conditions in a spark ignition gasoline engine and in a diesel engine, the need for improved conversion effectiveness has remained unsatisfied. Moreover, there is a continuing need for improved effectiveness in treating emissions from any combustion process, particularly for simultaneously treating the nitrogen oxides and soot particulate emissions from diesel engines. Several techniques have been proposed to modify the exhaust chemistry enabling the use of existing catalyst technology. However, these techniques can add considerable cost and complexity to the vehicle.

[0008] One technique that has been successfully applied in large stationary applications comprises injecting urea into the exhaust stream ahead of the catalytic converter where it quickly decomposes to ammonia. The ammonia reacts with NO and N0 ₂ in the exhaust stream on the catalytic converter surface to form N₂ and H₂O. Some of the challenges presented when using this technology include: (1) storing the aqueous urea solution onboard and preventing it from freezing under cold ambient temperature conditions; (2) correctly metering the urea solution into the exhaust (too much urea can result in ammonia emissions, too little urea can cause high NOx emissions); and (3) replenishing the urea—this requires establishing a supply network to distribute urea and customer acceptance of the expense and inconvenience in maintaining an adequate urea supply onboard the vehicle.

[0009] Another approach comprises adding a NOx adsorbent to the catalyst washcoat to adsorb NOx emissions from the exhaust stream during lean conditions. The adsorbed NOx must be periodically purged by shifting the air/fuel ratio from lean to slightly rich causing the adsorbent to release the adsorbed NOx which is reduced to nitrogen by the catalyst in the now rich exhaust stream. This technique presents significant control problems as the air and fuel rates must be simultaneously modified by the engine control system to effect the air-fuel ratio change without altering the engine load. The heterogeneous combustion diesel engine has an even more challenging additional problem of generating extremely heavy amounts of particulate emissions at air-fuel ratios near stoichiometric or rich conditions.

[0010] Particulate filters have been shown to be an effective means for controlling diesel particulate emissions. Wall flow particulate filters have been developed over the past twenty years and can be greater than 90% efficient in trapping particulate matter including nanoparticles. Such filters comprise endplugged honeycomb structures and are known as “wall flow” filters because the flow paths resulting from alternate channel plugging require the fluid being treated to flow through the porous ceramic cell walls prior to exiting the filter. The honeycomb structures have a portion of the cells plugged to allow better flow through the porous walls. A portion of the cells at the inlet end and outlet end (or face) are plugged in an arrangement wherein each cell is plugged only at one end. The preferred arrangement is to have every other cell on a given face plugged as in a checkered patter. The honeycomb structures may be made of any suitable material, such as ceramic, glass-ceramic, or metal. Especially preferred are ceramic materials, such as those that yield cordierite, mullite, or mixtures thereof on firing. The honeycomb structures are typically circular or square in cross-section. However, other shapes such as oval and rectangular may be suitable as dictated by the particular exhaust system.

[0011] The principle disadvantage with particulate filters is the need to periodically regenerate the filter to remove the trapped particulate matter. Regeneration removes particulate matter from the filter by oxidizing the carbon and volatile organic compounds (VOCs) to carbon dioxide and water. This oxidation occurs spontaneously at temperatures above about 600° C. Diesel exhaust temperatures are typically not hot enough to initiate spontaneous regeneration, particularly in light load operating conditions where exhaust temperatures may seldom exceed 200° C. Thus, a regeneration technique which is initiated at much lower temperatures and is controlled to limit the particulate filter temperature increase is required.

[0012] During particulate oxidation in the diesel particulate filter, some of the NO₂ created in an upstream non-thermal plasma reactor is converted back to NO. However, in order to get the most benefit from an NO₂ catalyst, the exhaust feedstream must be mostly NO₂.

[0013] There is a continuing need for improved effectiveness in treating emissions from any combustion process, particularly for treating nitrogen oxide and soot emissions from diesel engines.

SUMMARY OF THE INVENTION

[0014] A first embodiment of the present integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus is suitable for use with a short pulse power supply and comprises:

[0015] a wall flow-type substrate having an exhaust inlet, an exhaust outlet, and a plurality of parallel channels extending through the substrate;

[0016] the substrate having a plurality of layers arranged in an alternating fashion comprising a high voltage electrode layer; a ground electrode layer; and a filter layer disposed between the high voltage electrode layer and the ground electrode;

[0017] channels extending through the high voltage electrode layers and the ground electrode layers being plugged to prevent exhaust flow therein; and

[0018] channels extending through the filter layers serving as exhaust flow channels, a portion of the channels at the exhaust inlet ends and exhaust outlet ends being plugged in an arrangement wherein each channel is plugged only at one end;

[0019] wherein during operation of the apparatus, a plasma is generated in the filter layers and an exhaust stream to be treated enters at the exhaust inlet, flows through the filter channels and through the porous filter channel walls, and exits at the outlet as a treated exhaust stream;

[0020] whereby nitrogen oxides in the exhaust stream are converted in the plasma primarily to NO₂; particulate matter in the exhaust stream is captured in the porous channel walls; the filter is continuously regenerated by the plasma and the NO₂ formed in the plasma; and NO byproduct from the filter regeneration is converted back into NO₂ via plasma at the outlet ends of the exhaust channels.

[0021] A second embodiment of the present invention provides an apparatus suitable for use with a traditional high voltage alternating current power supply. The second embodiment of the present integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus comprises:

[0022] a wall flow-type substrate having an exhaust inlet, an exhaust outlet, and a plurality of parallel channels extending through the substrate;

[0023] the substrate having a plurality of layers arranged in an alternating fashion comprising a high voltage electrode layer; a ground electrode layer; and a filter layer disposed between the high voltage electrode layer and the ground electrode;

[0024] wherein said high voltage electrode layers and said ground electrode layers comprise dielectric barrier electrode layers;

[0025] channels extending through the high voltage electrode layers and the ground electrode layers being plugged to prevent exhaust flow therein; and

[0026] channels extending through the filter layers serving as exhaust flow channels, a portion of the channels at the exhaust inlet ends and exhaust outlet ends being plugged in an arrangement wherein each channel is plugged only at one end;

[0027] wherein during operation of the apparatus, a plasma is generated in the filter layers and an exhaust stream to be treated enters at the exhaust inlet, flows through the filter channels and through the porous filter channel walls, and exits at the outlet as a treated exhaust stream;

[0028] whereby nitrogen oxides in the exhaust stream are converted in the plasma primarily to NO₂; particulate matter in the exhaust stream is captured in the porous channel walls; the filter is continuously regenerated by the plasma and the NO₂ formed in the plasma; and NO byproduct from the filter regeneration is converted back into NO₂ via plasma at the outlet ends of the exhaust channels.

[0029] A combustion exhaust treatment system comprising the integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus includes the apparatus disposed in fluid communication with an exhaust outlet of a combustion device;

[0030] a high voltage power source connected to the integrated nonthermal plasma reactor-diesel particulate filter apparatus; and

[0031] a catalytic converter having a catalyst for reducing nitrogen oxides in an exhaust stream, the catalytic converter having an inlet connected to the integrated non-thermal plasma reactor-diesel particulate filter apparatus for receiving a plasma and particulate treated exhaust stream and an outlet for emitting a catalyst treated exhaust stream.

[0032] A method for treating particulate matter and nitrogen oxides in a combustion exhaust stream comprises:

[0033] passing a combustion exhaust stream through an integrated nonthermal plasma reactor-diesel particulate filter exhaust treatment apparatus including a wall flow-type substrate having an exhaust inlet, an exhaust outlet, and a plurality of parallel channels extending through the substrate;

[0034] the substrate having a plurality of layers arranged in an alternating fashion comprising a high voltage electrode layer; a ground electrode layer; and a filter layer disposed between the high voltage electrode layer and the ground electrode,

[0035] channels extending through the high voltage electrode layers and the ground electrode layers being plugged to prevent exhaust flow therein; and

[0036] a portion of the channels at the exhaust inlet end and exhaust outlet end being plugged in an arrangement wherein each channel is plugged only at one end;

[0037] generating a plasma in the filter layers wherein the exhaust stream to be treated enters at the inlet face, flows through the filter channels and through the porous channels walls, and exits at the outlet face as a plasma and particulate treated exhaust stream;

[0038] whereby nitrogen oxides in the exhaust stream are converted in plasma primarily to NO₂; particulate matter in the exhaust stream is captured in the porous channel walls; the filter layers are continuously regenerated by the plasma and the NO₂ formed in the plasma; and NO byproduct from the filter regeneration is converted back into NO₂ via plasma primarily at the outlet ends of the exhaust channels.

[0039] The present invention combines three major mechanisms for diesel particulate filter cleaning and NOx reduction. First, NO present in a diesel exhaust stream is converted to NO₂ inside the diesel particulate filter inlet channels. The converted NO₂ then reacts with trapped soot to clean the diesel particulate filter. Second, the trapped soot is also contained inside the plasma generated in the filter layers which also acts to keep the diesel particulate filter clean by direct carbon removal. Third, the exit channels of the diesel particulate filter are in plasma which converts any NO made from the diesel particulate filter regeneration back into NO₂ for reduction by an NO₂ catalyst.

[0040] The present invention provides the advantage of integration of two significant exhaust treatment functions into one. The present integrated non-thermal plasma reactor-diesel particulate filter apparatus provides the advantage of generating appropriate levels of NO₂ for providing reliable filter regeneration at a “low” temperature (below about 250° C.). In addition, the non-thermal plasma function of the integrated apparatus generates other species which may also contribute to the oxidation of soot at low temperatures. The invention eliminates the problem of NO back reactions in the diesel particulate filter which reduces deNOx catalyst functioning. Further, the present system is advantageously less complex and requires fewer components than previously known systems.

[0041] These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Referring now to the drawings, which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in the several Figures:

[0043]FIG. 1 shows an integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus in accordance with the present invention.

[0044]FIG. 2 is a top sectional view taken along the line 2-2 in FIG. 1 of a filter layer of the apparatus of FIG. 1.

[0045]FIG. 3 is a top sectional view taken along the line 3-3 of an electrode layer of the apparatus of FIG. 1.

[0046]FIG. 4 is a schematic diagram showing the apparatus of FIG. 1 in an engine exhaust system.

[0047]FIG. 5 shows a front inlet sectional view of an integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus in accordance with an alternate embodiment of the present invention.

[0048]FIG. 6 is a schematic diagram showing the apparatus of FIG. 5 in an engine exhaust system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0049] Turning now to FIG. 1, an integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus (integrated NTP-DPF apparatus) 10 includes a wall flow type diesel particulate filter substrate 12 having an exhaust inlet face 14, an exhaust outlet face 16, and a plurality of parallel channels 18 extending through the substrate 12 from the exhaust inlet 14 to the exhaust outlet 16. The term “wall flow type diesel particulate filter substrate” or “wall flow substrate” as used herein is meant to refer to an endplugged honeycomb structure of the type known in the art as “wall flow” filters since the flow paths resulting from alternate channel plugging require the fluid being treated to flow through the porous (typically ceramic) cell walls prior to exiting the filter The wall flow substrate 12 may be made of any suitable nonconductive porous material such as glass-ceramic or alumina. Especially suited are porous ceramic materials, such as those that yield cordierite, mullite or a mixture of these on firing. In a most preferred embodiment, the wall flow substrate 12 comprises cordierite.

[0050] The wall flow substrate 12 is divided into a plurality of three types of rows or layers arranged in an alternating fashion comprising a high voltage electrode layer 20; a ground electrode layer 22; and a filter layer 24 disposed between the high voltage electrode layer 20 and the ground electrode layer 22.

[0051] A portion of the channels 18 at the exhaust inlet face 14 and exhaust outlet face 16 are plugged in an arrangement wherein each channel is plugged only at one face. The unplugged channels 18 function as exhaust channels. In a preferred embodiment, blocked channels 26 in the filter rows 24 are plugged in an alternating, checkered type pattern. The filter rows 24 function as a wall flow diesel particulate filter.

[0052]FIG. 2 provides a top sectional view taken along the line 2-2 in FIG. 1 of the wall flow substrate 12 showing a filter row 24 and exhaust flow through the exhaust channels 18. As illustrated in FIG. 2, an exhaust stream 28 to be treated (arrows indicating exhaust flow) enters the filter rows 24 through the inlet face 14. The present apparatus may be advantageously employed to treat an exhaust stream from combustion devices such as, but not limited to, coal fired furnaces, oil fired furnaces, reciprocating internal combustion engines, gasoline spark ignition engines, diesel engines, or gas turbine engines. While the present invention may be advantageously employed to treat combustion exhaust streams generally, it is particularly suited for treating a diesel engine exhaust stream typically comprising particulates, HC, N₂, NOx (NO, NO₂), O₂, H₂O, CO, and CO₂. The exhaust gas 28 flows through the substrate channels 1 and channel walls 19 and exits the outlet channels 16 leaving the particulate stuck in the porous channel walls 19.

[0053] The channels 30 of the high voltage electrode rows 20 and ground electrode rows 22 are coated with a suitable metal conductor (not shown). A via 32 is drilled through each high voltage 20 and ground electrode 22 to form an electrical path to connect each cell as shown in FIG. 3. The channels 30 of each high voltage 20 and ground electrode 22 are then blocked 34 to prevent gas flow through the electrode channels. The channels 30 can be plugged with ceramic cement or similar material. The plug does not have to extend throughout the electrode channel 30 as long as both ends are plugged up to the electrode. In this way, particulates are trapped in adjacent flow channels 18 and the gases passing through the wall are forced into a plasma region and treated therein before exiting the device.

[0054] Bus bars 36 are used on the sides 38, 40 of the substrate 12 to connect the high voltage electrodes 20 and ground electrodes 22 using adequate isolation to prevent the formation of plasma forming in undesirable areas.

[0055] The integrated NTP-DPF apparatus 10 is connected to a high voltage power source by suitable electrical connections (not shown) that would be apparent to one of ordinary skill in the art. In a preferred embodiment, the power source comprises a short pulse power supply 42 that is applied to effect plasma formation between the high voltage electrode layers 20 and ground electrode layers 22 without the use of a dielectric material. When power is applied, the exhaust channels 18 extending through the filter layers 24 are in plasma. The exhaust stream 28 enters the channels 18 at the inlet face 14 and NOx present in the exhaust stream 28 is converted to NO₂. This NO₂then reacts with the particulate to form CO, CO₂, and NO, thus cleaning the diesel particulate filter by continuous regeneration. With the entire filter section in plasma, the particulate trapped in the porous channel walls is also removed directly.

[0056]FIG. 4 shows in block schematic form an embodiment of the present invention comprising an exhaust treatment system 44 including integrated NTP-DPF apparatus 10 connected to short pulse power supply 42. The system 44 includes a diesel engine 46 that generates a combustion exhaust stream 28 which includes NOx, N₂, particulate matter, HC, O₂, H₂O, CO, and CO₂. Diesel engine exhaust outlet 48 is connected to the inlet 14 of the integrated NTP-DPF apparatus 10 for receiving the combustion exhaust stream 28. During operation, the exhaust stream 28 is treated in the plasma generated in the filter layers 24 primarily to convert nitrogen oxides (NOx) to NO₂. The exhaust stream 28 flows through the filter channels 18 and through the porous channel walls 19 from the inlet 14 to exit at the outlet end 16. Particulate matter in the exhaust stream 28 is captured in the porous channel walls. The filter layers 24 are regenerated by the direct action of cleaning the particulate on the walls with the plasma and by the NO₂ formed in the plasma. Since the outlet portion 16 of the exhaust channels are also in plasma, any NO byproduct from the filter regeneration function is then converted via plasma at the outlet face 16 back into NO₂ for reduction by the NO₂ catalyst which follows. The plasma and particulate treated exhaust stream 50 passes from the outlet 16 of the integrated NTP-DPF apparatus 10 to a catalytic converter 52 having a catalyst for further treating the plasma treated exhaust stream 50, particularly for reducing nitrogen oxides in the plasma treated exhaust stream 50. The catalytic converter 52 has an inlet 54 for receiving the plasma treated stream 50 and an outlet 56 for emitting the catalyst treated exhaust stream 58.

[0057] Turning now to FIGS. 5 and 6, an alternate embodiment of the present integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus (integrated NTP-DPF apparatus) 60 suitable for use with a traditional alternating current type high voltage power supply is shown. The apparatus 60 employs alternating dielectric barrier layers 62 and alternating layers of a wall flow type diesel particulate filter substrate 12. The dielectric barrier material may include materials such as, but not limited to, dense cordierite, alumina, titania, mullite, plastic, and other high dielectric constant materials, or combinations thereof.

[0058] As in the first embodiment, the diesel particulate filter substrate 12 includes an exhaust inlet face 14, an exhaust outlet face 16, and a plurality of parallel channels 18 extending through the substrate 12 from the exhaust inlet 14 to the exhaust outlet 16, The diesel particulate filter substrate layers 12 are arranged in alternating fashion with a plurality of dielectric barrier electrode 64 layers 62 comprising high voltage electrode layers 66 and ground electrode layers 68.

[0059] Again, a portion of the channels 18 at the exhaust inlet face 14 and exhaust outlet face 16 are plugged in an arrangement wherein each channel is plugged only at one face. The unplugged channels 18 function as exhaust channels. In a preferred embodiment, blocked channels 26 in the filter rows 24 are plugged to provide an alternating, checkered type pattern. The filter rows 24 function as a wall flow diesel particulate filter.

[0060] In FIG. 6, the apparatus 60 is shown in an exhaust treatment system 70. The integrated NTP-DPF apparatus 60 is connected to a traditional alternating current high voltage power source 72 by suitable electrical connections (not shown) that would be apparent to one of ordinary skill in the art. The system 70 includes a diesel engine 46 in fluid communication with the integrated non-thermal plasma reactor-diesel particulate filter 60. A plasma and particulate treated exhaust stream 50 passes from the outlet 16 of the integrated NTP-DPF apparatus 60 to a catalytic converter 52 having a catalyst for further treating the plasma treated exhaust stream 50, particularly for reducing nitrogen oxides in the plasma treated exhaust stream 50.

[0061] While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims. 

1. An integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus 10 comprising: a wall flow-type substrate 12 having an exhaust inlet 14, an exhaust outlet 16, and a plurality of parallel exhaust channels 18 extending through said substrate 12; said substrate 12 having a plurality of layers arranged in an alternating fashion comprising a high voltage electrode layer 20; a ground electrode layer 22; and a filter layer 24 disposed between said high voltage electrode layer 20 and said ground electrode layer 22; electrode layer channels 30 extending through said high voltage electrode layers 20 and said ground electrode layers 22 being plugged to prevent exhaust flow therein; and a portion of said parallel channels 18 at exhaust inlet end 14 and exhaust outlet 16 being plugged 26 in an arrangement wherein each channel 18 is plugged only at one end; wherein during operation of said apparatus 10, a plasma is generated in said filter layers 24 and an exhaust stream 28 to be treated enters at said inlet 14, flows through said filter channels 18 and through porous channel walls 19, and exits at said outlet 16 as a treated exhaust stream 50; nitrogen oxides in said exhaust stream 28 being converted in said plasma primarily to NO₂; particulate matter in said exhaust stream 28 being captured in said porous channel walls 19; said filter layers 24 being continuously regenerated by said plasma and by said NO₂ formed in said plasma; and NO byproduct from said filter generation being converted back into NO₂ via plasma at said outlet ends 16 of said exhaust channels
 18. 2. The apparatus 10 of claim 1, wherein said wall flow substrate 12 is made of cordierite.
 3. The apparatus 10 of claim 1, wherein alternating channels 26 in said filter layers 24 are plugged to provide a checkered-type pattern of plugged channels 26 and unplugged exhaust channels
 18. 4. The apparatus 10 of claim 1, wherein said exhaust stream 28 to be treated comprises an exhaust stream from a coal fired furnace, an oil fired furnace, a reciprocating internal combustion engine, a gasoline spark ignition engine, a diesel engine, or a gas turbine engine.
 5. The apparatus 10 of claim 1, wherein said exhaust stream to be treated 28 comprises a diesel engine exhaust stream.
 6. The apparatus of claim 1, comprising: high voltage electrode layers 66 and said ground electrode layers 68 comprising dielectric barrier electrode layers 62 to provide an integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus
 60. 7. A combustion exhaust treatment system 44 comprising: the integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus 10 of claim 1, said apparatus 10 being in fluid communication with an exhaust outlet 48 of a combustion device 46; a short pulse power source 42 connected to said integrated nonthermal plasma reactor-diesel particulate filter apparatus 10 and a catalytic converter 52 having a catalyst for reducing nitrogen oxides in an exhaust stream, said catalytic converter 52 having an inlet 54 connected to said integrated non-thermal plasma reactor-diesel particulate filter apparatus 10 for receiving a plasma and particulate treated exhaust stream 50 and an outlet 56 for emitting a catalyst treated exhaust stream
 58. 8. A combustion exhaust treatment system 70 comprising: the integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus 10 of claim 1, having high voltage electrode layers 66 and ground electrode layers 68 comprising dielectric barrier electrode layers 62 to provide an integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus 60, said apparatus 60 being in fluid communication with an exhaust outlet 48 of a combustion device 46; an alternating current power source 72 connected to said integrated non-thermal plasma reactor-diesel particulate filter apparatus 60; and a catalytic converter 52 having a catalyst for reducing nitrogen oxides in an exhaust stream, said catalytic converter 52 having an inlet 54 connected to said integrated non-thermal plasma reactor-diesel particulate filter apparatus 60 for receiving a plasma and particulate treated exhaust stream 50 and an outlet 56 for emitting a catalyst treated exhaust stream
 58. 9. A method for treating particulate matter and nitrogen oxides in a combustion exhaust stream 28 comprising: passing a combustion exhaust stream 28 through an integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus 10 comprising: a wall flow-type substrate 12 having an exhaust inlet 14, an exhaust outlet 16, and a plurality of parallel exhaust channels 18 extending through said substrate 12; said substrate 12 having a plurality of layers arranged in an alternating fashion comprising a high voltage electrode layer 20; a ground electrode layer 22; and a filter layer 24 disposed between said high voltage electrode layer 20 and said ground electrode 22; electrode layer channels 34 extending through said high voltage electrode layers 20 and said ground electrode layers 22 being plugged to prevent exhaust flow therein; and a portion of said exhaust channels 18 at said exhaust inlet 14 and said exhaust outlet 16 being plugged in an arrangement wherein each exhaust channel 18 is plugged only at one end; generating a plasma in said filter layers 24 of said apparatus 10 wherein said exhaust stream 28 to be treated enters at said inlet 14, flows through said exhaust channels 18 and through porous channels walls 19, and exits at said outlet 16 as a plasma and particulate treated exhaust stream 50; whereby nitrogen oxides in said exhaust stream 28 are converted in said plasma primarily to NO₂; particulate matter in said exhaust stream 28 is captured in said porous channel walls 19; and said filter layers 24 are continuously regenerated by said plasma and by said NO₂ formed in said plasma; and NO byproduct from said filter generation are converted back into NO₂ via plasma primarily at said outlet ends 16 of said exhaust channels
 18. 10. The method of claim 9, wherein said wall flow substrate 12 is made of cordierite.
 11. The method of claim 9, wherein alternating exhaust channels 18 in said filter layers 24 are plugged to provide a checkered-type pattern of plugged channels 26 and unplugged exhaust channels
 18. 12. The method of claim 9, wherein said exhaust stream 28 to be treated comprises an exhaust stream from a coal fired furnace, an oil fired furnace, a reciprocating internal combustion engine, a gasoline spark ignition engine, a diesel engine, or a gas turbine engine.
 13. The method of claim 9, wherein said exhaust stream to be treated 28 comprises a diesel engine exhaust stream.
 14. The method of claim 9, further comprising: further treating said plasma and particulate treated exhaust stream 50 in a catalytic converter 52 having a catalyst for reducing nitrogen oxides in an exhaust stream; said catalytic converter 52 having an inlet 54 connected to said integrated non-thermal plasma reactor-diesel particulate filter apparatus 10 for receiving said plasma and particulate treated exhaust stream 50 and an outlet 56 for emitting a catalyst treated exhaust stream
 56. 15. The method of claim 9, wherein said integrated nonthermal plasma reactor-diesel particulate filter exhaust treatment apparatus 10 comprising is powered by a short pulse power supply
 42. 16. The method of claim 9, wherein said high voltage electrode layers 66 and said ground electrode layers 65 comprise dielectric barrier electrode layers 62 providing an integrated non-thermal plasma reactor-diesel particulate filter
 60. 17. The method of claim 9, wherein said high voltage electrode layers 66 and said ground electrode layers 65 comprise dielectric barrier electrode layers 62 providing an integrated non-thermal plasma reactor-diesel particulate filter 60; and wherein said integrated non-thermal plasma reactor-diesel particulate filter exhaust treatment apparatus 60 is powered by an alternating current power supply
 72. 